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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 171 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.604 + 99 =
  2. 2.53 − 19 =
  3. 3.60 − 19 =
  4. 4.60 + 19 =
  5. 5.652 + 99 =
  6. 6.65 + 29 =
  7. 7.417 + 99 =
  8. 8.78 + 19 =
  9. 9.36 − 19 =
  10. 10.44 − 9 =
  11. 11.20 + 9 =
  12. 12.17 + 29 =
  13. 13.14 + 29 =
  14. 14.62 + 9 =
  15. 15.24 − 9 =
  16. 16.272 − 99 =
  17. 17.27 − 9 =
  18. 18.24 + 19 =
  19. 19.77 − 29 =
  20. 20.81 − 19 =
  21. 21.35 + 9 =
  22. 22.61 + 9 =
  23. 23.48 + 29 =
  24. 24.759 − 99 =
  25. 25.28 + 19 =
  26. 26.99 − 29 =
  27. 27.50 + 19 =
  28. 28.328 − 99 =
  29. 29.21 + 19 =
  30. 30.75 + 9 =
  31. 31.26 + 19 =
  32. 32.64 + 19 =
  33. 33.24 + 29 =
  34. 34.70 + 29 =
  35. 35.435 + 99 =
  36. 36.30 + 9 =
  37. 37.49 − 19 =
  38. 38.34 + 9 =
  39. 39.30 + 29 =
  40. 40.57 − 9 =

Answer key

  1. 703
  2. 34
  3. 41
  4. 79
  5. 751
  6. 94
  7. 516
  8. 97
  9. 17
  10. 35
  11. 29
  12. 46
  13. 43
  14. 71
  15. 15
  16. 173
  17. 18
  18. 43
  19. 48
  20. 62
  21. 44
  22. 70
  23. 77
  24. 660
  25. 47
  26. 70
  27. 69
  28. 229
  29. 40
  30. 84
  31. 45
  32. 83
  33. 53
  34. 99
  35. 534
  36. 39
  37. 30
  38. 43
  39. 59
  40. 48

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